The aim of the proposed research is to define certain basic properties of normal human arylsulfatase A (cerebroside sulfate sulfohydrolase). Of special interest are those properties which may serve as the reference point for identifying aberrations in mutant forms of arylsulfatase A in the metachromatic leukodystrophies. There are at least four types of this genetic disorder, and the evidence suggests that in each type a different form of mutant enzyme is produced. Characterization of the specific aberrations would provide a rational basis for designing approaches toward prophylactic and/or therapeutic interventions. Pure normal human urinary arylsulfatase A will be prepared by a protocol developed in this laboratory. The enzyme will be used for characterization studies and for preparing chemically modified derivatives. The properties to be characterized include enzyme kinetics, substrate specificity, amino acid composition, carbohydrate composition, subunit make up and peptide mapping. Modifications will include covalent attachment of substituents to reactive groups of the enzyme, removal of sugar residues, and conjugation to macromolecular matrices. The properties sought in the modified enzyme include increased stability, enhanced activity, resistance to proteolysis, and altered affinity for specific cell membranes. BIBLIOGRAPHIC REFERENCES: Fluharty, A.L., Stevens, R.L., Miller, R.T., Shapiro, S.S., and Kihara, H. Ascorbic Acid-2-Sulfate Sulfohydrolase Activity of Human Arylsulfatase A. Biochim. Biophys. Acta, 429:408-516, 1976. Stevens, R.L., Fluharty, A.L., Killgrove, A.R., and Kihara, H. Microheterogeneity of Human Arylsulfatase A on Isoelectric Focusing. Fed. Proc., 35:1726, 1976.